Ah yes, the T-rex 600 is a very nice electric heli for sure. Please ensure you keep doing very regular maintanance on that one (Which I'm sure you do..) and if you haven't already get the entire rotorhead upgraded to metal, the mixing arms and things going onto the washout especially.
My team mate's been flying a 600 for longer than I can remember now and have had good luck with it so far except for the few small incidents where one was the ever popular failure of the plastic parts. I think they've been fortunate however to not lose a battery in one of the crashes. The big electrics are nice, performance is pretty great if you go the route they've gone and blinged it with a big Hacker motor and good Thunderpower batteries but I'll pass on an electric this size and flying style (3D) simply because of the "what if the battery get's damaged in a crash" factor. It's just too expensive to take care of crash costs along with battery replacement costs. On top of that at this size battery damage is much more likely because of the inertia from the size of model.
I think my good friend Ade Law from the UK has a good take on these things when he says the helis more in the Hirobo Lepton size should be the ticket for guys like me and him that wanna go out put it all on the line and still be able to do it without the "what if" factor clogging up the brain. Compass models that produce the ever popular Knight .50 is bringing out a new machine in this size which looks absolutely incredible. Of course I'm a bit partial to JR machines for many reasons so I'm actually considering the new Voyager E they've got going now...that size electric seems more feesable for something that might bite it regularly.
For guys that don't crash often and prefer a more sporty style of flying (Loops, rools, normal aeros and the occasional flip) I do however feel a bigger size electric is all good. Especially if you maybe go to A123's in this scenario. We've tested the A123's on my mate's T-rex and they work a charm for mild 3D and sport flying, that changes everything when it comes to the whole flying a big electric thing.
Now coming more to my previous post's comments. I will however any day convert my Sylphide .90's to electric if the spare cash starts lying around, the entire JR F3C team has converted their Sylphides over now and for F3C I think that's the way to go also. No more fiddling with getting the most power out of the machines, plug in and fly only worrying about getting the scores up there. Of course on helis this style it's more feesable for me because we never take unnecissary(sp?) risks with them...whole different ballgame but yeah our estimated cost for conversion of the machines is running in excess of R15k for each heli so it might be a while before we actually do it.

In the planes however...I wouldn't even consider electric for one of my .40~1.20 sized 3D profiles, they just see too much action (yes crash wise also) so the good ol OS/Saito is IMHO the ticket. On smaller planes like the foamies and things nothing other than electric of course, the inertia is low enough and through the 50+ crashes I've had with 3D foamies I've never lost a battery. On something like my 5 meter scale Nimbus glider of course I'm going to try going electric, pricey powerplant but it's in a lower risk enviroment so it's feesable for me. Bigger aerobatic planes I'm going for gas, nothing tops the sound, maybe a smoker and the smell...on this size gas motor's reliability and ease of use is excellent also so no need for electric to get around cleaning and fiddling.
So yea as you can see, for me it all depends on the application. I'm sure as prices on the electris stuff changes and the technology gets even better all the above would also with time change. But if things are going to get any cheaper than it currently is, I doubt.